Precision operator for an aircraft autothrottle or autopilot system with engine performance adjust

ABSTRACT

An autothrottle system for an aircraft includes a motor, actuator assembly, and position sensor operatively connected between the motor and a moving portion of the actuator assembly. An electronic controller is configured to control the motor to move the actuator assembly to actuator positions based at least on position information from the position sensor to move the throttle lever to lever positions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/900,542, entitled “Precision Operator for an Aircraftautothrottle or Autopilot System With Engine Performance Adjust” filedFeb. 20, 2018, and U.S. patent application Ser. No. 15/554,642, entitled“Precision Operator for an Aircraft autothrottle or Autopilot SystemWith Engine Performance Adjust” filed Aug. 30, 2017, which is a nationalphase of PCT Application No. PCT/US2016/045002, entitled “PrecisionOperator for an Aircraft autothrottle or Autopilot System,” filed Aug.1, 2016, and claims priority to U.S. Provisional Patent Application No.62/336,200, entitled “Precision Operator for an Aircraft autothrottle orAutopilot System,” filed May 13, 2016, and U.S. Provisional PatentApplication No. 62/250,819, entitled “Precision Operator for an Aircraftautothrottle or Autopilot System,” filed Nov. 4, 2015; all of which areincorporated herein by reference in their entirety.

FIELD THE INVENTION

The disclosed embodiments relate to an aircraft autopilot system. Inparticular, the disclosed embodiments relate to a precision operator foran aircraft autopilot system, and more specifically to an arrangement bywhich selective control for automated mechanical adjustment of aircraftthrottle controls and/or aircraft flight control surfaces can beeffected while accommodating ready manual override of the automatedoperator when deemed necessary or otherwise at the behest of the pilotor other operator of the aircraft. Specifically, the autothrottle willhandle a rapid decrease or increase of power in a regulated mannerdespite a vehicle operator's attempt to override the autothrottle incertain situations, such as a go round.

BACKGROUND OF THE INVENTION

Aircraft flight decks have become increasingly sophisticated and rely toa large extent on technology and automated controls that havesignificantly reduced pilot workload and enhanced systems reliabilityand efficiency and, as such, passenger safety. In addition to advancednavigation capabilities provided by, for example, GPS and graphicaldisplays that contribute to greatly improve situational and operationalstatus awareness, advances in autopilot systems have proven oftremendous assistance to pilots in maintaining both aircraft control andthe smooth and efficient operation of those aircraft that are providedwith such capabilities.

Autopilot systems provide functions that range from, at the lowest endof the range of capabilities, simple wing leveling to, in more advancedsystems, aircraft directional and course control to maintain and track aselected course, altitude maintenance and adjustment control, andadjustments to the aircraft throttle(s) to maintain and effect desiredchanges in aircraft velocity.

Automated control of the aircraft throttle(s), in particular, presentsspecial problems that have, in the past, limited such capabilities toonly the largest or, at least, the most technologically complex andadvanced aircraft, such as large commercial airline passenger jets,advanced regional and general aviation jets, and high-end turbinepropeller airplanes. Such autothrottles provide the ability to realizetruly automated, hands-off control of the aircraft, thus providingincreased aircraft operating efficiencies, reducing cost in, forexample, the consumption of fuel, and vastly decreasing pilot workloadand thereby notably increasing flight safety. But providing autothrottlecapabilities in an aircraft requires, with the technologies currently inuse, physical, spatial and mechanical accommodations that limit thisfunctionality to only the largest and/or most technologically advancedaircraft which, in most cases, must be designed and constructed toinclude and utilize autothrottle functionality.

In most aircraft, the throttle(s)—which are selectively adjustable tocause the engine(s) to generate a predetermined amount of power orthrust to propel the aircraft at a desired velocity—are adjusted bypilot-controlled manual override displacement of one or more graspablehandles on levers that are pivotally mounted for rotation through alimited arc in a throttle quadrant in the aircraft cockpit or flightcontrol deck. These levers are typically connected to the engines orengine controllers by control cables that are longitudinally displacedas the positions of the throttle levers are pivotally adjusted.

In almost any aircraft, not insignificant forces must be applied to thethrottle levers—whether manually by a pilot or by an operating motor ofan autothrottle system—to vary or adjust the pivoted positions of thelevers. The motors of the system, therefore, must be fairly robust, bothin size and weight (to provide sufficient torque and operating forcesapplied to the throttle lever) and in construction (to assure continuedreliability through tens of thousands of activations and operations). Asa consequence, only aircraft specifically designed and constructed withsufficient clearances and space to accommodate these motors andassociated elements at, in and/or alongside the throttles quadrant ofthe cockpit, and capable of accepting the significant additional weightassociated with these systems and their component parts, are able toincorporate such autothrottles into and with their flight controls.There is moreover virtually no ability to retrofit or add autothrottlecapabilities into existing aircraft that have not already been speciallydesigned and constructed to accommodate the associated operatingcomponents of an autothrottle system.

It is in addition important, to assure safe operation of the aircraftunder continued control by the pilot, that the pilot can quickly andeasily override or otherwise assume manual control of the throttles froman activated autothrottle system in the event that operating conditionsin the aircraft may suddenly require that the pilot assume immediatephysical control of the throttles, as in an emergency or anycircumstance in which the pilot deems it appropriate, without having tofirst manually disengage the autopilot or autothrottle system(s). Suchcircumstances, however may have a detrimental result in that suddenpilot engagement may cause operations of the aircraft throttle controloutside of a desired throttle range. Such an occurrence can lead to slowengine responses or even a stalling condition at a worst case scenario.Accordingly, an improved autothrottle is beneficial to deter or preventpilot operation of an autothrottle outside of a desired operating range.

SUMMARY OF THE INVENTION

The disclosed embodiments are directed to an aircraftautopilot/autothrottle operator arrangement that is compact,lightweight, reliable and readily installable in an aircraft, even inaircraft in which no special accommodation for adding or providingautopilot/autothrottle capabilities have been designed into or providedfor the aircraft, and which can be safely and easily overridden by apilot wishing to quickly assume manual control of the throttle(s) whenunder the control of the autopilot/autothrottle system. The disclosedembodiments provide such an operator arrangement that can also beapplied, with like advantageous functionality, as part of or inconjunction with an aircraft autopilot system to control the movementsof control surfaces of the aircraft whose variable positions areadjustable to control, for example, the pitch, roll and yaw of theaircraft. Additionally, the autothrottle can be used anywhere that anengine has to be controlled. For example, the autothrottle can beadapted to control a drone, an engine driving an oil rig, and the like.

The disclosed embodiments provides an aircraft autopilot/autothrottleoperator that exhibits a number of significant advantages over thosecurrently in widespread use. First, the inventive arrangement isrelatively lightweight, especially as compared to currentautopilot/autothrottle operating arrangements and components. Second,the inventive arrangement is notably simplified, as compared to currentautopilot/autothrottle operating arrangements, which can providesignificant increases in physical and operating reliability. Third, theinventive arrangement is notably more compact than currentautopilot/autothrottle operating arrangements and is thereforeinstallable in a wider range of aircraft of widely varying size. Fourth,the inventive arrangement is based on the use of a linear operator thatis activated from a position remote from the throttle handle pivot, thusallowing its installation—either at the time of initial construction oras an add-on or retrofit to an existing structure—in aircraft having arelatively compact throttle quadrant or that have not otherwise beenspecially designed to accommodate a conventional autopilot/autothrottleand its heavy-duty motors and clutches and which would otherwise bemounted at and proximate the pivot points of the throttle handles.Fifth, the actuator utilized in the inventive arrangement does notrequire separate or integrated clutches or clutch components and insteadprovides inherent override capabilities, and neither does it require aseries of gears between an operating motor and its attachment to thethrottle handle—thereby greatly decreasing complexity, weight andphysical space requirements and increasing operating reliability.

In one aspect, the disclosed embodiments provide an autopilot systemincluding a motor configured to impart rotational movement to a shaftextending from the motor, the motor being mounted on a support. Anactuator assembly is operatively connected to the shaft and to anattachment end of a throttle lever, the throttle lever having a controlend, opposite to the attachment end, for application of manual force. Aposition sensor is operatively connected between the motor and a movingportion of the actuator assembly. The system further includes anelectronic controller configured to control the motor so that it movesthe actuator assembly to actuator positions based at least in part onposition information received from the position sensor to cause movementof the throttle lever to lever positions. The actuator assembly includesa bearing assembly having a plurality of bearings configured to contacta surface of the shaft for converting rotational movement of the shaftinto linear motion of the bearing assembly along the shaft. The actuatorassembly further includes a shuttle arm having a mounting surface at afirst end configured to attach to the bearing assembly and at least onelinkage arm at a second end of the shuttle arm which is operativelycoupled to the attachment end of the lever.

The disclosed embodiments may include one or more of the followingfeatures. The actuator assembly may be configured so that manualmovement of the control end of the throttle lever applies a thrust forceto the distal end of the shaft relative to the bearing assembly; andwhen the thrust force exceeds a threshold, the bearing assembly isconfigured to slip along the shaft irrespective of any rotation that maybe concurrently imparted to the shaft by the motor.

The bearing assembly may be configured to accept the shaft in athroughbore thereof and may include at least one set of bearings, eachof the bearings being supported in the bearing assembly to contact thesurface of the shaft at determined angles relative to a longitudinalaxis of the shaft so as to trace a helical pattern on the surface of theshaft as the shaft moves through the bearing assembly.

The at least one linkage arm at the second end of the shuttle arm may berotatively coupled to the attachment end of the throttle lever, the atleast one linkage arm being positioned parallel to the shaft to allowfree movement of a distal end of the shaft as the bearing assembly movesalong the shaft.

The system may be installed in an aircraft having two engines and thethrottle lever of each engine may be controlled separately. In the eventof an engine loss, the power setting of the remaining engine iscontrolled to stay above stall speed and is further controlled not toexceed an engine power threshold. The engine power threshold may bebased at least in part on a maximum power imbalance that can becompensated by action of an aircraft rudder to prevent unwanted rotationof the aircraft.

According to one aspect of the invention, when an engine loss occurs,the autothrottle provides haptic feedback to indicate to the pilotwhether throttle should be increased or decreased.

According to one aspect of the invention, the autothrottle enables fullpower usage during takeoff while monitoring engine balance and yaw.

According to one aspect of the invention, the autothrottle uses reducedpower during landing, specifically an efficient level of power tostabilize the aircraft's approach.

According to one aspect of the invention, the autothrottle monitorsground speed and wind speed. If ground speed and wind speed are notequal, a controller of the autothrottle determines if a wind shearcondition exists. If a wind shear condition exists, an alarm isactivated and the autothrottle is disconnected. According to one aspectof the invention ground speed is determined using GPS.

According to one aspect of the invention a wind shear condition existsif ground speed and wind speed differ by at least 15 knots.Alternatively, or in addition, outside temperature can be monitored todetermine if a wind shear condition exists. If the outside temperaturedecreases, the autothrottle can be disabled whereupon the pilot willresume control of the aircraft. Alternatively, or in addition, winddirection is monitored continually on field approach. An abrupt changein wind direction of speed indicates a wind shear condition. An abruptchange is a change in less than 30 seconds.

The disclosed embodiment also implements a method by which anautothrottle adjusts engine performance to substantially conform topreferred performance parameters. One or more sensors monitor engineperformance. An engine controller, typically implemented with amicroprocessor and memory uses data from the sensors to detect acondition wherein an actual engine performance differs from a preferredengine performance, referred to as a nonconforming condition. One suchcondition is a surge condition. Haptic feedback is provided via athrottle lever until the actual engine performance matches the preferredengine performance. Preferably, the haptic feedback nudges the stick inthe desired direction to correct the fault condition.

According to one aspect of the invention, the autothrottle isautomatically engaged when a nonconforming condition is detected.

According to one aspect of the invention, a tension required to adjustthe throttle lever(s) is increased or decreased based at least in parton the nonconforming condition.

According to one aspect of the invention the auto-throttle acts at andon power lever cables going to the engine. The autothrottle can alsoprovide FADEC type engine protection. The actuator can be mounted on theengine at the cable attachment point. This adaptation has heretofore notbeen adapted because of the bulk of conventional auto-throttles and thehigh temperatures around the engine, especially after shutdown. Thepresent implementation uses a stepper motor and therefore lends itselfto remotely mounting the electronic control in a more moderate, nearbyenvironment. The disclosed linear actuator has an instinctively safeclutch assuring manual override. The actuator shuttle would act directlyon or near the power cable attachment to the fuel control valve. It willback drive the power lever in the cockpit. The stepper motor is mountedwith the motor drive circuitry in the existing interface protection box.Additionally, an accordion protection sleeve is provided on the rotatingdrive shaft to protect it from oil and fluids contamination.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages will become more apparentand more readily appreciated from the following detailed description ofthe disclosed embodiments taken in conjunction with the accompanyingdrawings of which:

FIG. 1 is an elevated perspective view of an aircraft autothrottleoperator and associated elements constructed in accordance with anembodiment of the disclosed invention;

FIG. 2 is a side view of the embodiment of the autothrottle operatordepicted in FIG. 1;

FIG. 3 is a perspective view of a second embodiment of the aircraftautothrottle operator with a housing cover removed;

FIG. 3A is a partial perspective view of another embodiment of theaircraft autothrottle operator;

FIG. 4 is an enlarged view of the bearing assembly and shaft of theembodiment of the autothrottle depicted in FIG. 3;

FIG. 5 is a side view of the embodiment of the autothrottle operatordepicted in FIG. 3;

FIG. 6 is a flow chart illustrating a method for operating anautothrottle system for an aircraft; and

FIG. 7 is a schematic representation of a segment of a flight path.

DETAILED DESCRIPTION

The disclosed autothrottle is configured to move an aircraft's powerthrottles using independent linear actuators, typically located in thethrottle quadrant and commonly attached to the throttle power handle atits connection to the throttle cable. According to one aspect of theinvention, an actuator functions by rotating a hardened, precisionground, and polished stainless steel shaft that carries an actuationshuttle, which is the heart of the throttle control. The actuationshuttle typically carries two sets of three precision ball bearingsmounted at a rotation axis angle relative to the shaft axis. The outerraces of the bearings roll on the shaft, moving the shuttle along theshaft at a rate proportional to the shaft diameter and the bearing axisangle. The shuttle's thrust is proportional the coefficient of frictionbetween the outer race of the spring loaded ball bearings and the shaft.The shuttle moves accurately along the shaft, much like a threadedlead-screw, but without the threads. It slips at a very repeatablethrust force that is proportional to the spring tension in the bearingcarrier. This controlled breakaway force assures that the flight crewcan maintain backlash-free control of the engine power even with acatastrophic malfunction of any of the actuator's components and withouthaving to disengage a clutch. Under manual operation, the throttlescause the shuttle to rotate the brushless motor. This requires precisesequencing of the stator winding to rotate, thereby obviating a drivemotor runaway.

An autothrottle computer monitors the engine internal temperature, theturboprop's torque or EPR/N1 in a turbofan engine, gas generator speed,prop speed, air data, GPS position, GPS velocity, battery voltage, andthe like. The autothrottle computer uses this data to control the thrustand protect the engines from damage. The power lever controls the enginethrust to control speed while maintaining safe speeds and safetemperatures.

The autothrottle has various operating modes including at least atakeoff mode, a climb mode, an airspeed hold mode, one or moreprotection modes, an engine out mode, an automatic speed selection mode,a simultaneous speed mode selection, and a windshear sense.

In takeoff mode, the throttles are advanced to a predetermined thrust,or optionally based on alternative limiting factors to a differentthrust. The computer monitors the engine power as the throttles areadvanced. The command is reduced if the engine starts to surge or exceedthe thrust/torque limit due to ram air.

In climb mode, the throttles are maintained at maximum torque/thrust forthe maximum allowed time, typically 3-5 minutes. The throttles are thenautomatically reduce to a maximum continuous climb or torque schedule(PWC) as a function of altitude. In this mode, the aircraft autopilot'sSPEED-ON-ELEVATOR can be engaged. The autothrottle protects the enginefrom over temperature and/or over torque. As the aircraft climbs tohigher altitudes, the temperature (TIT) will increase and thetemperature protection mode will become active. The temperatureprotection mode adjusts thrust to limit the temperature to a maximumcontinuous temperature. The climb thrust is maintained as the aircraftlevels off at cruise altitude or until commanded to change value orMode.

The airspeed hold mode controls airspeed to at a commanded or presetvalue by a manual mode selection change or automatically by an FMS. Theautothrottle will maintain the selected airspeed through climb ordescent, except as may be limited by maximum torque, temperature, oraltitude rate. The autothrottle can be enabled to limit IAS to 250 knotsbelow 10,000 feet, automatically based on GPS location. The airspeed canbe set by an FMS airspeed input, which facilitates RTA and RNPoperations that require multiple speed changes. The control computer canbe configured to automatically set approach speeds based on aircraftgross weight. In addition, commanding missed approach with a TOGA buttoncan automatically set TO/GA thrust while maintaining engine protection.

Various protection modes are constantly monitoring aircraft performanceand engine performance. The engines are monitored and limited to theestablished safe torque and temperature limits. The airspeed iscontrolled at both under-speed and over-speed including VMO/MMO.Additionally, the AOA can be monitored. The autothrottle can also beconfigured to compensate for bank angle at low airspeeds.

An engine out mode (Vmca mitigation mode) monitors for a loss of anengine (OEI) on a multiengine aircraft, which can result in hazardousyaw at speeds below Vmca. The autothrottle computer continually monitorsmultiple engine parameters and will detect a loss of engine bytriggering on: N1 (compressor turbine) nominally below 40% and oilpressure nominally below 10 psi with auto-feather active. The computercomputes the amount of rudder authority loss due to the reduction ofairflow over the rudder. Vmca is the minimum control speed in thetake-off configuration, a.k.a. air minimum control speed or minimumcontrol speed in free air.

Haptic throttle handle vibration is used to alert the flight crew withOEI and IAS below Vmca, if a thrust of a remaining engine exceeds aMaximum Allowable Thrust. A body rate yaw sensor detects an onset ofadverse yaw and will initiate the haptic crew alert to provide anadditional margin of safety to compensate for weight or configuration.The haptic vibration is direction sensitive, such that it will increasethe force necessary to further advance the throttle in over speed,over-torque or over-temperature. The haptic vibration can be configuredto hinder further advance and deliberately retard the throttles untilthe exceedance is cleared. Also, the throttles will be hindered fromfurther reduction with an under-speed or AOA warning and deliberatelyadvance to eliminate an impending hazardous condition.

An automatic thrust control may be user enabled in takeoff mode that isinitiated by a loss of an engine, with the airspeed below Vmca+3 knots.This automatic control will retard the operating engine to a definedthrust/. The computer will monitor a yaw input and if the yaw exceeds 5degrees when in OEI and at or below VMCa+3 IAS, the computer reduces thethrust of the good engine to mitigate the yaw.

Automatic speed selection can be user activated to automatically set theappropriate Maneuvering speed for turbulence penetration and/or Vref forapproach speeds based on gross weight. It should be noted that asimultaneous speed mode selection of the autothrottle and Autopilotspeed hold is not permitted. If the autothrottle detects simultaneousattempts to control speed-on-elevator, the autothrottle will disconnectand the pilot will receive an alert. The alert can be a visual and/or aspeaker/headphone audio alert.

Finally, windshear sense is an algorithm that monitors ground speed (GS)versus airspeed (IAS) and ambient temperature (SAT). When the aircraftis in landing configuration with gear and flaps deployed, a rapidincrease of IAS vs GS disconnects the autothrottle to prevent automaticthrust reduction. The disconnect alerts the flight crew with an audioand/or visual alert.

FIGS. 1 and 2 present two views of an embodiment of the precisionaircraft autothrottle operator. The autothrottle operator system orarrangement, identified in the drawing figures by the general referencenumeral 10, is attached for use to a conventional throttle handle orlever 12 of an aircraft. The throttle lever 12, the configuration andconstruction of which is conventional, is mounted for pivoted movementor displacement about a shaft or other pivot point or fulcrum 14 atwhich the lever 12 is secured in place at the throttle quadrant (notshown) of the aircraft. The distal end 16 of throttle lever 12 isconfigured for ease of grasping and manipulation, to advance and retardthe lever 12 through its arcuate range of displacement, by a pilotmanually controlling the power output of the associated aircraft engineand, thereby, the airspeed or velocity of the aircraft. The opposite orproximal end 18 of throttle lever 12 connects at attachment pin or shaftor point 20 at one end of a cable 22 that itself connects, generally atits far end, to the engine or engine controller associated with lever12. Thus, pilot manipulation, i.e., counterclockwise (in the figures)advancement or clockwise retarding—of the lever distal end 16 aboutpivot point 14 causes opposite-sense arcuate motion of attachment point20, thus effecting linear displacement of cable 22 and correspondingchanges in the power output of the associated engine. Aircraftimplementations in which the motion-transmitting functionality of cable22 is instead provided by other elements or systems are known in theart, but changes in the power or thrust generated by an aircraft engineare in any event generally controlled in accordance with senseddisplacement of the proximal extension of the corresponding throttlelever.

The autothrottle operator of the embodiment depicted in FIGS. 1 and 2 isformed by an actuator assembly 24, a motor 26, and a position sensor 28.

In particular implementations, actuator assembly 24 comprises anarrangement formed of a bearing assembly 30 (also referred to herein asshuttle body 30), an elongated shaft 32 and a linear fork 34.

The combination of bearing assembly 30 and shaft 32 function to convertrotary motion into linear displacement. In the embodiment depicted inthe figures, this functionality is implemented using acommercially-available assembly identified by its manufacturer,Zero-Max, Inc. of Plymouth, Minn. as a Roh'lix Linear Actuator. Sixrolling-element bearings 36, in sets of three, are supported in a baseblock 38 at predetermined angles about a throughbore 40 defined in block38 and through which shaft 32 extends for longitudinal displacement ofblock 38 along the shaft (a more detailed view of the block 38 and shaft32 can be seen in FIG. 4, which is discussed below in the context of thesecond embodiment). Each of the bearings 36 contacts the surface ofshaft 32 at an angle, such that the bearings 36 trace a helical patternalong the shaft and thereby longitudinally displace block 38 along theshaft as the shaft is rotated. Put another way, as the shaft 32 isrotated, i.e., by selective operation of motor 26, the bearings 36 traceout an imaginary screw thread, causing linear longitudinal displacementof block 38 on and along shaft 32. Base block 38 is constructed as twohalves that are coupled by the combination of springs 42 and associatedscrews 44 that are adjusted to selectively setting the thrust force thatbearings 36 apply to and against shaft 32 and, correspondingly, theamount of linear force that must be manually applied to the block 38 toovercome the thrust force and allow the bearings 36 to sliplongitudinally along the surface of shaft Thus, when the thrust forcesset or provided by a predetermined adjustment of screws 44 are exceeded,block 38 slips on and along shaft 32 irrespective of any rotation thatmay be concurrently imparted to the shaft by, e.g., motor 26.

With continued reference to FIGS. 1 and 2, the operatively-rotated shaftof motor 26 is coupled to the end of shaft 32 remote from block 38. Themotor 26 may be, for example, a precision stepper motor that steps inresponse to the input of pulses or other electrical signals from adiagrammatically-depicted controller 48 through 200 consecutive rotativepositions spaced about 1.8 degrees apart. Motor 26 is operable toincrementally (i.e., step-wise) rotate bidirectionally, i.e.,selectively in both/either the clockwise and/or counterclockwisedirections, based on the operating signals from controller 48. One ormore gears may optionally between the motor shaft and shaft 32 if neededor desired to attain a rotational speed of shaft 32 deemed suitable forthe particular implementation and/or aircraft. Motor 26 is mounted on amotor bracket 46 having an opening 47 for unimpeded passage of shaft 32and/or the motor shaft, bracket 46 being itself securable to a fixedstructure in the aircraft cockpit to secure the motor 26 againstmovement as it operatively rotates shaft 32.

Controller 48 may by way of illustration comprise an electroniccontroller having a processor and memory dedicated to the operation ofmotor 26 and, optionally, also to associated elements and functionalityof the inventive autothrottle system, or its functionality may beincorporated in or as a part of the control system or elements of anautopilot system or of a flight management system or of other avionicsand/or automation systems of the aircraft.

Linear fork 34 connects shuttle block 38 to throttle lever attachmentpoint 20. Fork 34, which may be implemented as a unitary element (asdescribed below in the context of the second embodiment), comprises inthe illustrated embodiment a shell or tray 50 to which block 38 issecured, a pair of opposed linkage arms 52 that are rotatively coupledat one of their ends to attachment point 20 of the throttle lever, and aweb 54 that joins tray 50 to arms 52. The free end portion 56 of shaft32 that is opposite its coupled connection to motor 26 is freely movablethrough and relative to apertures, passages and voids and the like thatare defined in web 54 to accommodate the shaft end 56 as shuttle block38 is operatively displaced or “shuttles” along shaft 32.

The current relative displacement or position of shuttle block or body38 along the elongation of shaft 32 is determined by monitoring changesin the distance or spacing between, by way of illustration, thepositionally-fixed motor 26 and the movable shuttle body 38. To providethis functionality, in the illustrated embodiment the position sensor 28is implemented by a linear potentiometer 58, such as, for example, anMLP miniature linear potentiometer manufactured by Celesco TransducerProducts, Inc. of Chatsworth, Calif., that is connected as a positionsensor between motor bracket 46 (to which the motor is secured) and tray50 (on which the shuttle body is mounted). Potentiometer sensor 58 iselectrically connected to controller 48 which thereby monitors changesin the linear position of shuttle body 38 (and thus, correspondingly, ofthe attachment point 20 at the proximal end of the throttle lever) onand along shaft 32. The throttle position is accurately mapped andrecorded using the potentiometer sensor 58 when the system is installedin the aircraft. Because the linear actuator is controlled with astepper motor, a map of the throttle position for an individual step isdetermined and used as a means of detecting un-commanded movement orslip in the movement due to obstruction of the throttle lever. Inparticular embodiments, such detection could ultimately result in thesystem disengaging the autothrottle.

FIGS. 3-5 depict a second embodiment of the aircraft autothrottleoperator. In this embodiment, the shuttle block 38 is connected to thethrottle lever attachment point 20 by a shuttle arm 34′ which isimplemented as a unitary element, rather than a dual-pronged fork 34, asdiscussed above (the controller 48 is not shown in these views). Theshuttle arm 34′ has a shell or tray 50′ at one end thereof to whichblock 38 is secured. The tray 50′ is oriented so that a mounting surfaceof the bearing assembly 30 is oriented in a vertical plane, whereas inthe first embodiment, the mounting surface is oriented in a horizontalplane. The motor 26 may be held in place at a pivoting joint of abracket 41 which can be attached to an interior structure of anaircraft. A detailed view of the block 38 and shaft 32 can be seen inFIG. 4. In FIG. 3, the cover of the housing 39 containing the block 38is not shown so that the block 38 can be seen in the figure. FIG. 5shows the housing 39 with its cover in place. At the distal end of theshuttle arm 34′ is a linkage arm 52′ which is rotatively coupled toattachment point 20 of the throttle lever. The distal, i.e., free endportion 56, of shaft 32 that is opposite its coupled connection to motor26 is parallel to the linkage arm 52′ and therefore can move freely asshuttle block 38 is operatively displaced or “shuttles” along shaft 32.

In operation, the autothrottle System requires a throttle positionsignal from a throttle position sensor. As discussed above, the sensoris a linear potentiometer that is read by analog to digital converter inthe Engine data concentrator. In one embodiment, a very precise opticalposition sensor can replace the linear potentiometer. The opticalposition sensor uses a laser beam projected on a white target that ismonitored by a photo diode array. The diode array sensor usestriangulation of the position of the target relative to the source andsensor, to determine throttle position. The non-contact implementationof this optical sensor eliminates a risk of obstruction of movement ofthe throttle levers. The basic actuator mechanism is, by its nature, notsubject to malfunction that would lock up the throttle.

In the alternative embodiment shown in FIG. 3A, an optical sensor isused in place of the linear potentiometer 58. Alternatively, both theoptical sensor and the linear potentiometer can be used to provideredundancy. The current relative displacement or position of shuttleblock or body 38 along the elongation of shaft 32 is determined bymonitoring changes in the distance or spacing between, by way ofillustration, the positionally-fixed motor 26 and the movable shuttlebody 38. To provide this functionality, in the illustrated embodimentthe position sensor is implemented by an optical distance sensor havinga transmitter 28B and an receiver 28C, such as, for example, a CMOSdistance measuring sensor that is connected as a position sensor tomeasure a distance between motor 26 and tray 50′ (on which the shuttlebody is mounted). Alternatively, the optical distance Sensor can bemounted to the motor bracket 41. In a preferred embodiment, a reflectoris mounted to the tray 50′ or another suitable component.

One skilled in the art would appreciate that the locations of theelements can be reversed so that the transmitter 28B and receiver 28Care arranged at the tray 50′ and the reflector is arranged at the motor26, the motor bracket 41, or another suitable component. The opticalsensor 28B, 28C is electrically connected to the controller 48 whichthereby monitors changes in the linear position of shuttle body 38 (andthus, correspondingly, of the attachment point 20 at the proximal end ofthe throttle lever) on and along shaft 32. The throttle position isaccurately mapped and recorded using the optical sensor 28B, 28C whenthe system is installed in the aircraft. Because the linear actuator iscontrolled with a stepper motor, a map of the throttle position for anindividual step is determined and used as a means of detectingun-commanded movement or slip in the movement due to obstruction of thethrottle lever. In particular embodiments, such detection couldultimately result in the system disengaging the autothrottle.

The basic manner of operation of the inventive autothrottle operator 10,to selectively control an aircraft throttle in an automated operatingmode (e.g. under the control of an autopilot system), will now bedescribed. In response to electrical signals from controller 48, steppermotor 26 is operated to selectively rotate coupled shaft 32 in a desireddirection (to respectively increase or decrease engine thrust) and, asshaft 32 rotates, shuttle body 38 is linearly displaced along andrelative to shaft 32 as the bearings 36 trace a helical path along thesurface of rotating shaft 32. This linear displacement of shuttle body38 is transferred through linkage fork 34 to throttle lever 12 atattachment point 20, causing throttle lever 12 to pivot about itsfulcrum 14, just as though throttle lever 12 were being manually movedabout fulcrum 14 by a pilot grasping its distal end 16. The resultingdisplacement of attachment point 20 at the proximal end 18 of throttlelever 12 likewise causes linear displacement of engine control cable 22,thus causing the engine to vary the power output or thrust of theaircraft engine associated with that throttle lever. Thus, as shuttlebody 38 is displaced along shaft 32 toward motor 26, throttle lever 12is rotated counterclockwise (in the Figures) to reduce engine power and,as shuttle block 38 is displaced along shaft 32 away from motor 26,throttle lever 12 is rotated clockwise to increase engine power—again,just as though the throttle lever were being manually adjusted by apilot grasping the throttle lever at its distal end 16.

Changes in the linear position of shuttle body 38 relative to motor26—and, correspondingly, of the rotative position of the throttle lever12—can be determined by controller 48 by monitoring the output of thepotentiometer position sensor 58, as can the current position of theshuttle body. However, since it is the function of an autothrottle tovary engine output power to, for example, attain and/or maintain apredetermined airspeed, controller operation of motor 26 to increase ordecrease engine power is dependent not so much on the absolute positionor relative spacing of shuttle block 38 and motor 26 but, rather, onwhether an increase or decrease in engine power (and, thus, whetheroperation of motor 26) is needed to provide the desired airspeed;accordingly, monitoring of the output of position sensor providesfeedback to controller 48 for use in, inter alia, confirming properoperation of the autothrottle system.

An important and highly advantageous feature of the inventiveautothrottle system 10, as compared to conventional commercialautothrottle arrangements, is the provision of override capabilitieswithout the use of clutches and their associated apparatus andconnections. The capability of the inventive system 10 to be easilyoverridden for manual pilot control of the throttle(s), when the system10 is engaged and even while it remains so, is an important and inherentfeature of the system 10 and its construction. By physically graspingthrottle lever 12 at its distal end 16 and applying sufficient force toadvance or retard the throttle, shuttle body 38 is caused (by itscoupled connection to the proximal end 18 of lever 12) to slip or slidelongitudinally along shaft 32, thus providing manual pilot control ofthe throttle even if controller 48 were to remain operationallyactivated to effect rotation of the motor and shaft 32. Of course, it isgenerally intended that, when manual manipulation of throttle lever 12is initiated, autothrottle controller 48 will normally be, automaticallydeactivated from continued operation of motor 26, but the ability toreadily assume manual control of the throttle in the event of, forexample, a systemic or component failure to easily and immediatelyoverride the autothrottle functionality presents a particularlynoteworthy improvement in assuring failsafe operation of the aircraft.

As previously described, pilot-effected manual override of theautothrottle arrangement requires that the pilot advance or retard thethrottle lever 12 with a force that, at a minimum, exceeds the thrustforce that the bearings 36 apply to the surface of shaft 32. Since thatthrust force is adjustable by selective rotation of adjustment screws 44of shuttle body 38, in particular implementations of the inventivearrangement the thrust force is preset to assure that manual override bythe pilot is readily available using a reasonable magnitude ofpilot-applied force that is deemed suitable for the particularapplication and for assuring continued safe operation of the aircraft.Setting of the bearings thrust force to a magnitude sufficient to assurelinear movement of shuttle body 38 along and in response to rotation ofshaft 32 will provide both reliable automated autothrottle control ofthe throttle and manual override control using reasonable pilot-appliedforces on the throttle lever.

For example, a stepper motor contemplated for use in the inventiveautothrottle assembly operatively generates a fairly high torque thatrotates the shaft 32 to produce, for example, about 12 pounds of torqueon the engine throttle control cable 22 (i.e., at the proximal end 18 ofthrottle lever 12) and about 4 to 6 pounds of force at the distal end 16of throttle lever 12. This means that, in a typical intendedimplementation of the system 10, the aircraft pilot can easily overridethe autothrottle simply by pushing or pulling back, with a force of atleast the same 4 to 6 pounds, on the distal end 16 of the throttle levereven if the motor 26 is engaged and operatively rotating the shaft 32and/or even if the entire assembly is frozen. By manually applying tothe throttle lever a force of about or in excess of, e.g., 4 to 6pounds—which is a relatively small amount not appreciably greater thanthe force required to manually adjust the throttle lever without anengaged autothrottle—the shuttle body 38 will slip on and longitudinallyalong shaft 32 whether or not the shaft is being rotated by motor 26 andthe pilot will thereby immediately obtain full, unconstrained andunconditional manual control of the throttle. The autothrottlearrangement thus presents an inherently safe system that assures a pilotthe ability to readily assume manual control of the aircraft throttle(s)at any time. When combined with or forming an element of an aircraftautopilot system, the autothrottle arrangement 10 provides anintrinsically safe ability to quickly and easily override the forcesapplied by the autothrottle controller and the autopilot—instructedoperations.

The inventive autothrottle arrangement can also be implemented toprovide a warning to a pilot in the event that the aircraft isdetermined to be operating, for example, at too high or too low anairspeed for the current operating conditions or maneuvers of theaircraft. As is known, stepper motors such as the motor 26 generallycontemplated for inclusion in the system 10 have (e.g.) three coilswhich are, in normal use, selectively actuated to cause the motor tobidirectionally rotate its shaft from step to step. In accordance withthis embodiment, haptic feedback can be applied to the throttle lever,i.e., in the nature of “stickshaker” functionality—when the controller48 determines, e.g. by monitoring at least the aircraft airspeed, thatthe airspeed is approaching the bounds or limits of a predeterminedrange of values.

Thus, if the controller 48 determines that the aircraft's increasingairspeed is approaching a predetermined safety limit value (e.g. themaximum structural cruising speed of the aircraft), or that itsdecreasing airspeed is approaching a predetermined minimum limit value(such as the minimum controllable airspeed or stall speed of theaircraft), motor 26 can be operated to cause the throttle lever tooscillate or shake and thereby alert the pilot to the impending unsafeoverspeed or underspeed condition. Similarly, by monitoring enginetorque, controller 48 can likewise provide a warning to the pilot byapplying like haptic feedback through the throttle handle 12 if it isdetermined that the engine is at or approaching an unsafe operatingcondition, e.g. excessive torque.

This functionality is implemented by selectively applying electricalsignals to individual ones or combinations of the multiple actuatingcoils of the motor, for example by activating only two of the threecoils, or rapidly cycling electrical signals to a selected one or moreof the motor coils- and does not require that, at the time of suchhaptic warning, the autothrottle must be or have been engaged or activeto autocontrol the throttle and, thereby, the engine power. Thus, forpurposes of this pilot-warning functionality the inventive autothrottlesystem 10 provides “always-on” sensing and haptic alert capabilities. Inany event, if controller 48 senses that no manually-input changes to theposition of throttle lever 12 have been applied in response to itshaptic warning, the system 10 can be configured to operatively adjustthe engine power or torque to correct the airspeed or overtorquecondition by suitable motor-driven rotation of shaft 32 and theresulting linear displacement of shuttle body 38 as explainedhereinabove.

Accordingly, by implementing this functionality the system 10 can beviewed as always engaged, with controller 48 continuously monitoringrelevant characteristics and operating conditions of the aircraft thatmay warrant or necessitate a warning—delivered with haptic feedbackdelivered by shaking or oscillating or vibrating the throttle lever 12and/or the initiation of automated controlled movement of the throttlelever by operation of motor 26 to correct or ameliorate the out ofbounds condition.

Another advantageous feature of the inventive autothrottle arrangementis realized in an aircraft having, for example, two (or more) throttlelevers each controlling the power output of a corresponding engine. Insuch multi-engine aircraft, manual control of airspeed, throughmanipulation of the throttle levers, is effected by concurrentlyadvancing (or retarding) the two (or more) throttle levers. An issuethat can arise in manual pilot control of the throttles of suchmulti-engine aircraft is that if the multiple throttle levers are notadjusted together, i.e., so that each lever is advanced or retarded byabout the same amount, the engines may produce different levels of poweror torque, as a result of which the propulsion of the aircraft may beunbalanced with one engine producing more thrust or torque than another,as the engine on one wing is producing less (or more) thrust than theengine on the other wing. Similarly, operating characteristics of oneengine, with respect to another engine of the aircraft, may result ineach engine generating different amounts of thrust or torque even if therespective throttle handles are correspondingly positioned or adjusted.

In a multi-engine aircraft in which an inventive autothrottle system 10is provided for each of the engines, an imbalance of the thrust ortorque produced by the two (or more) engines can be sensed and used bythe controller(s) 48 to warn or alert the pilot of the imbalance byhaptically shaking or vibrating (or the like) one or both/all of thethrottle levers, using the procedure described hereinabove. Aspreviously noted, this functionality does not require that theautothrottle system 10 be in operational use to autocontrol thepositions of the throttle levers and, correspondingly, to automaticallyvary or adjust the thrust or power output of the engines. In addition,as also described above, the system can be configured so that detectionthat the multiple engines are out of sync or not generating the samelevels of thrust or torque will cause the autothrottle system 10 of oneor more of the engines to automatically readjust the correspondingthrottle lever(s) 12 and thereby equalize the relevant operatingcharacteristics of the multiple engines.

Another advantageous application of the inventive autothrottlearrangement in multi-engine aircraft is warning of and preventing theapplication of too much thrust to, for example, one of the two engineswhen one engine fails or is otherwise determined to be generating lessthan the intended, or expected, thrust. In a (by way of illustrativeexample) two engine aircraft, the manufacturer will have established anairspeed, VMCA, as the minimum controllable airspeed on a single enginewhen the aircraft is airborne, i.e., the minimum airspeed at which, withonly one of the two engines operating, the pilot will have sufficientrudder authority to prevent the aircraft from yawing to an extent thatwill cause the aircraft to, in effect, roll over and dive into theground. Thus, the failure—or degraded performance—of one engine inflight creates an asymmetric thrust condition requiring that the pilotof a multi-engine aircraft immediately level off, apply significantrudder and increase power to the remaining engine to maintain anairspeed at or above VMCA. And where the aircraft airspeed is, when oneengine fails, below VMCA—such as in the landing phase of flight whenengine power is generally brought back to a fraction of full power orthrust—the application of too much power to the engine that remains inoperation will create a dangerous asymmetry in thrust and adverse yawfrom which the application of rudder may not enable a safe recovery.

Accordingly, in this further use of the inventive autothrottlearrangement, controller 48 monitors (at least) the current airspeed(and, preferably, the acceleration) of the multi-engine aircraft andcontinuously calculates, for single engine operation, the maximum safeor allowable thrust that should or can be placed on the remaining engineunder current flight and operating conditions. Put another way, thecontroller 48 continuously calculates, for the current airspeed belowVMCA, the allowable power limit (i.e., the maximum safe or permissiblegenerated thrust) for the remaining engine for that airspeed. If thepower or thrust being produced by that remaining engine, in accordancewith the position of throttle lever 12, is increasing and approaching(or at or beyond) the calculated maximum thrust that the engine shouldbe permitted to produce at the current airspeed, an alarm or warningwill be generated by the inventive arrangement 10 by vibrating oroscillating the engine's throttle lever 12 (as described hereinabove) toalert the pilot of the impending or existing over-throttle condition.

If the position of throttle lever 12 is not manually adjusted by thepilot in response to the alert, then the motor 26 of the inventiveautothrottle arrangement 10 may under appropriate conditions be operatedto adjust the position of the throttle lever (and thus retard thethrottle) under control of the system 10, without pilot input andirrespective of whether the autothrottle system 10 had theretofore beenoperatively controlling the aircraft throttles, and thereby avoid orterminate the over-throttle condition of the operating engine.

This functionality can also be applied to assist the pilot in manuallyadvancing the throttle, in response to the failure of the other engine,by only that amount appropriate to avoid an over-throttle condition ofthe remaining engine, by providing haptic feedback (by vibrating oroscillating the throttle lever 12) as the allowable thrust limit for theengine is approached; the pilot can proceed to manually advance thethrottle lever until it starts to vibrate and, as the aircraft airspeedbegins to increase, continue to manually advance the throttle leveruntil, again, the autothrottle system 10 resumes vibration of thethrottle lever. Since the controller 48 is continuously calculating anddetermining an increasing maximum allowable engine thrust as theairspeed increases, the pilot can continue to manually adjust thethrottle lever 12 in accordance with the vibration, or lack thereof,applied to the throttle lever by the autothrottle system 10. In thismanner the pilot is continuously guided in manually adjusting thethrottle so that the engine is always operating to generate the maximumsafe thrust based on the current airspeed and other relevant flight andenvironmental factors that the controller 48 can monitor.

For this and other implementations and applications of the inventiveautothrottle system, the system can itself adjust or vary or scale themagnitude of such haptic vibrations or oscillations of the throttlelever as a function of the urgency of the need for pilot action—so that,for example, the system applies relatively small magnitude vibrations tothe throttle lever as the limit value of airspeed or thrust or the likeis first approached, with vibrations of increasing magnitude applied tothe throttle lever as the limit value continues to be approached and isreached or exceeded.

Accordingly, by implementing this functionality the system 10 can beviewed as always engaged, with controller 48 continuously monitoringrelevant characteristics and operating conditions of the aircraft. By,for example, such monitoring, the inventive autopilot system isadditionally configured to provide additional advantageous modes ofoperation, as set forth below.

For example, the system 10 may be configured to provide a Speed HoldMode. In the speed hold mode the system 10 adjusts the engine thrust toachieve and maintain the selected airspeed.

The system 10 also may be configured to provide a Torque Control Mode,in which the system 10 is configured to adjust the engine thrust toachieve and maintain the selected engine torque.

The system 10 also may be configured to provide a Temperature LimitControl Mode. In this mode, the engine thrust is adjusted to achieve andmaintain the selected engine turbine inlet temperature.

The system 10 also may be configured to provide an Engine Protectionmode in which the system 10 will adjust engine thrust to keep enginetorque, speed and temperature from exceeding pre-defined targets in allmodes of operations. In particular embodiments, the autothrottle may beconfigured to protect the engine from exceeding the limits for one ormore of the following: torque, shaft horsepower, engine and propellerspeeds, engine temperature, engine pressure ratio.

The system 10 also may be configured to provide a Speed Protection Mode.In this mode, at all times the autopilot system protects the aircraftfrom over-speed or under-speed by adjustment of the engine thrust.

The system 10 also may be configured to provide a mode in which, duringmanual manipulation of throttles, if the throttles are moved too rapidlyby the pilot such that it could result in an engine power surge, theautopilot mechanism provides a warning to the pilot, e.g., by vibratingthe throttle lever.

The system 10 also may be configured to provide a turbulence penetrationmode that, when engaged by the pilot, automatically adjusts the power toachieve a turbulence penetration speed calculated based on gross weightand aerodynamic characteristics of the aircraft.

The system 10 also may be configured to provide a mode in which approachand take off speeds are calculated and entered into the speed controlmode of the autothrottle. Landing approach speed is typically calculatedas a function of gross weight and stall margin and may also includefactors such as, for example, wind speed and flap configuration. Thesystem 10 may also calculate and control airspeed to maintain optimumLift over Drag (L/D), e.g., by using an average Angle Of Attack (AOA)from the aircraft AOA sensor.

The system 10 also may be configured to provide multiple autothrottlemodes, such as, for example, automatic, airspeed control, and angle ofattack control. In automatic mode, the autothrottle flies the airplaneat maximum speed by controlling to the torque limit during initial takeoff and climb until the temperature becomes critical, at which point theautothrottle controls the engine to the maximum allowed temperature. Inparticular embodiments the autothrottle may be configured to protect theaircraft from out of limit conditions for one or more of the following:minimum airspeed; maximum angle of attack; and maximum airspeed undernormal and turbulence conditions.

The system 10 also may be configured so that when it is installed withan engine that has no protection mechanism such as a full-authoritydigital engine control (FADEC), the autopilot monitors critical engineparameters, such as, for example, temperature, speed pressure ratio,torque, horse power, etc., and acts to prevent these parameters fromexceeding the maximum values.

The system 10 also may be configured so that in the event of an enginepower loss in a two engine aircraft, the autopilot manages the powersetting of the remaining engine to stay above stall speed. At the sametime the system controls the remaining engine to maintain safe operatingconditions. In one embodiment, in the event of engine loss the throttlelever for the stalled or inoperative engine will vibrate or provideother haptic feedback to the pilot that the subject throttle lever hasno effect.

In one embodiment, the autothrottle addresses a problem occurring fromgas generator surges during throttle increase; which is a problemoccurring, for example, on Pratt & Whitney turboprops. Specifically, theautothrottle tailors throttle lever performance and response to match orsubstantially correspond to an ideal or preferred engine performancecurve. The autothrottle can be configured to monitor conditions andprovide haptic feedback, assume control, be disengaged, or the like.

For turboprops, the prop is turned by blowing hot gas over a turbine.Sudden throttle increase may cause gas generator surges, which causesuneven engine performance. Thus, the throttle needs to be delicatelyincreased to alleviate this problem, according to one aspect of theinvention, the autothrottle will automatically resist pilot manipulationof the throttle lever based on monitoring of engine performance andother parameters, thereby making it more difficult for manual control ofthe throttle lever until an existing gas surge dissipates. It should benoted that the autothrottle will provide haptic feedback orautomatically increase throttle lever response if the throttle lever ismoved too slowly. If a gas surge condition is detected and theautothrottle is not yet engaged, the autothrottle will automaticallyengage to counteract the surge condition. Alternatively or in addition,the autothrottle will provide a haptic warning such as vibration of thethrottle lever when a surge condition is detected without engaging thethrottle.

More particularly, the autothrottle feature will control an increase inthe throttle in a regulated manner. This is helpful because the responseof the engine is nonlinear such that small increases or decreases ofthrottle level result in relatively large and disproportionate powerchanges. Thus, by “mapping” the power performance of the engine and thenusing that information for throttle control, the throttle can beautomatically controlled to optimally perform over the different regionsof the engine's power output performance curve. For instances in whichthe autopilot is not engaged, as the engine performance deviates fromthe preferred performance curve, the autothrottle will provide hapticfeedback to the pilot via the throttle lever to signal to the pilot toadjust the throttle until the throttle engine performance is bought backinto alignment with the preferred performance curve of the engine.

In one embodiment, the autothrottle will automatically retard the levermotion to scale the lever motion based on a monitoring of the engineuntil the gas surge dissipates. In one embodiment, the midrange isslowed down until the surge dissipates. Alternatively, if theautothrottle is not engaged or an autothrottle override is engaged,haptic feedback is provided until the surge condition dissipates.Typically, this situation arises during landing, specifically during alanding abort. When landing is aborted and the aircraft has to makeanother attempt, the power needs to be increases quickly. However, thiswill create a power surge which can lead to temporary engine failure.The autothrottle will control the power increase in a regulated mannerand engage in high stress situations, such as an aborted landingattempt. A mapping of throttle position and power identifies the problemissues and regulates the response to avoid surge conditions.

In one embodiment, as the engine performance deviates from theperformance curve the autothrottle increases or decreases lever tensionas required to make the throttle lever easier or harder to adjust sothat the engine performance returns to an optimal point on theperformance curve. Additionally or alternatively, when the engineperformance deviates from the performance curve, a haptic or otherwarning is provided. Additionally or alternatively, the autothrottle canbe automatically engaged or disengaged.

In an aircraft in which an inventive autothrottle system 10 is present,a surge can be sensed and used by the controller(s) 48 to warn or alertthe pilot of the surge by haptically shaking, vibrating, or the like, ofthe throttle lever(s), using the procedure described hereinabove. Aspreviously noted, this functionality does not require that theautothrottle system 10 be in operational use to autocontrol thepositions of the throttle levers and, correspondingly, to automaticallyvary or adjust the thrust or power output of the engines. Rather, thesystem can be configured so that detection of a surge will cause theautothrottle system to automatically adjust the corresponding throttlelever(s) 12 to control the relevant operating characteristics of theengines. Alternatively, the system can be configured so that detectionof a surge will cause the autothrottle system to provide haptic feedbackto the corresponding throttle lever(s) 12.

The application of the inventive autothrottle arrangement provideswarning of and substantially prevents the surge condition. Controller 48monitors (at least) the current airspeed (and, preferably, theacceleration) of the aircraft and continuously calculates the maximumsafe or allowable thrust that should or can be placed on the engineunder current flight and operating conditions. In other words, thecontroller 48 continuously calculates, for the current airspeed belowVMCA, the allowable power limit (i.e., the maximum safe or permissiblegenerated thrust) for the engine for that airspeed. If the power orthrust being produced by that engine, in accordance with the position ofthrottle lever 12, is increasing and approaching (or at or beyond) thecalculated maximum thrust that the engine should be permitted to produceat the current airspeed, an alarm or warning will be generated by theinventive arrangement 10 by vibrating or oscillating the engine'sthrottle lever 12 (as described hereinabove) to alert the pilot of theimpending or existing surge condition.

FIG. 6 is a flow chart for method for operating an autothrottle systemfor an aircraft. The method includes monitoring engine performance of anaircraft engine (S10). When a gas surge is detected (S20), theautothrottle system is automatically engaged (S30). In one embodiment,the monitored engine performance is compared to a power performancecurve of the aircraft engine (S40). The autothrottle provides hapticfeedback to an aircraft pilot via a throttle lever until the monitoredengine performance matches the preferred engine performance (S50).According to one aspect of the invention, the haptic feedback comprisesincreasing or decreasing a throttle lever tension. The autothrottlemanipulates the throttle lever in a regulated manner until an existinggas surge dissipates (S60). The manipulating of the throttle lever isbased on the monitoring of engine performance until the existing gassurge dissipates.

It should be noted that the disclosed autothrottle can be used withFADEC (Full authority digital engine control) engines. Using hapticfeedback the autothrottle is configured to drive the motor two smallsteps, about twelve thousandths of an inch, against the motion that isgoing to cause a fault condition or an out-of-limits condition and thenone step back so that the throttle actually progresses against thepilot's manual motion. The throttle control will vibrate and actuallypush against the pilot. The pressure is not so strong that it cannot beoverridden, if necessary. However, the autothrottle is configured toactually pushes back and move the throttle, slowly, moderately, torestore an in-limits condition.

In one embodiment, haptic feedback is used to alert the pilot when he isin V/MC (velocity for minimal controllable air speed) location mode. Onapproach the pilot would feel a vibrating in his throttle handle andretard the throttle until the vibration stops. Once the vibration stops,the throttle can be advanced until it starts vibrating then back it offa little bit. The same thing he could use in takeoff because a pilot canpush the throttle forward and then if he starts getting close to theV/MC point it would vibrate and he would draw it back until thevibration stops. Alternatively, can the autothrottle can engageautomatically.

As discussed in more detail below, the autothrottle wind sheardetection, which prevents the throttle from being retarded in a windshear condition, namely, a head wind coming at the aircraft that appearsto make the air speed go up but in fact causes ground speed to go down.When the separation of ground speed and air speed increases theautothrottle would not retard the throttle to conserve the energy,because the aircraft is entering a wind shear condition.

As discussed in detail above, the autothrottle moves the aircraft powerthrottles by independent linear actuators, typically located in thethrottle quadrant and commonly attached to the throttle power handle atits connection to the throttle cable. According to one aspect of theinvention, the actuator operates by rotating a hardened, precisionground, and polished stainless steel shaft that carries an actuationshuttle as components of the throttle control. The actuation shuttletypically carries two sets of three precision ball bearings mounted at arotation axis angle relative to the shaft axis. The outer races of thebearings roll on the shaft moving the shuttle along the shaft at a rateproportional to the shaft diameter and the bearing axis angle. Theshuttle's thrust is proportional the coefficient of friction between theouter race of the spring loaded ball bearings and the shaft. The shuttlemoves accurately along the shaft, much like a threaded lead-screw, butwithout the threads. It slips at a very repeatable thrust force that isproportional to the spring tension in the bearing carrier. Thiscontrolled breakaway force assures that the flight crew can maintainbacklash-free control of the engine power, even in the event of acatastrophic malfunction of any of the actuator's components and withouthaving to disengage a clutch. Under manual operation, the throttlescause the shuttle to rotate the brushless motor. This intrinsically safemotor requires precise sequencing of the stator winding to rotate,thereby obviating a drive motor runaway.

According to one aspect of the invention, the autothrottle computermonitors the engine internal temperature, the turboprop's torque orEPR/N1 in a turbofan engine, gas generator speed, prop speed, air data,GPS position, GPS velocity, battery voltage, or the like. Theautothrottle uses this information to control the thrust and protect theengines from damage. The power lever controls the engine thrust tocontrol speed while maintaining safe speeds and safe temperatures.Haptic feedback can be used to signal when a change is required.

In a take off mode, the throttles are advanced to a predetermined thrustor optionally to a setting based at least in part on alternativelimiting factors. The computer monitors the engine power as thethrottles are advanced and the command is reduced if the engine startsto surge or exceed the thrust/torque limit due to ram air.

In climb mode, the throttles are maintained at maximum torque/thrust forthe maximum allowed time, typically 3-5 minutes and then automaticallyreduce to a maximum continuous climb or torque schedule (PWC) as afunction of altitude. In this mode, the aircraft autopilot'sSPEED-ON-ELEVATOR can be engaged, while the autothrottle protects theengine from over temperature or over torque conditions. As the aircraftclimbs to higher altitude, the temperature (TIT) will increase and thetemperature protection mode will become active to adjust the thrust tolimit the temperature at the maximum continuous temperature. The climbthrust is maintained as the aircraft levels off at cruise altitude oruntil commanded to change value or Mode.

In an airspeed hold mode, the autothrottle controls airspeed to at acommanded value by a manual mode selection change or automatically by aFMS. The autothrottle will maintain the selected airspeed through climbor descent, except as may be limited by maximum torque, temperature, oraltitude rate. The autothrottle can be enabled to limit IAS to 250 knotsbelow 10,000 feet, automatically based on GPS location. The airspeed canbe set by a FMS airspeed input. This facilitates RTA and RNP operationsthat require multiple speed changes. The control computer can beconfigured to automatically set approach speeds based on aircraft grossweight. In addition, commanding missed approach with the TOGA button canautomatically set TO/GA thrust while maintaining engine protection.

A protection mode of the autothrottle is constantly monitoring theaircraft performance and engine performance. The engines are monitoredand limited to the established safe limits in torque and temperature.The airspeed is controlled at both under-speed and over-speed includingVMO/MMO. Additionally, the AOA can be monitored as well. The autopilotis further configured to compensate for bank angle at low airspeeds.

The autothrottle preferably includes an “engine out mode” (VmcaMITIGATION). A loss of an engine (OEI) on a multiengine aircraft canresult in hazardous yaw at speeds below Vmca. In one embodiment, yawrate sensors are monitored to indicate an asymmetrical thrust condition.Generally, one engine will be retarded to correct for an undesired yaw.The autothrottle computer continually monitors multiple engineparameters and will detect a loss of an engine by triggering on: N1(compressor turbine) nominally below 40%, and oil pressure nominallybelow 10 psi with auto-feather active.

The computer computes the amount of rudder authority loss due to thereduction of airflow over the rudder. The autothrottle uses the rudderauthority loss to execute the necessary reduction in thrust from theremaining engine to prevent hazardous yaw by the relationshipMax thrust*(IAS/(Vmca+3)){circumflex over ( )}2.

As an example with IAS=72 k and Vmca=88+3 k(75/91){circumflex over ( )}2=63% of Max torque

Maximum allowable torque to prevent hazardous yaw=0.63*2230=1400 ft-lbs.

As discussed above, the system a throttle handle with haptic feedback.Haptic feedback can be used to alert the flight crew with OEI and IASbelow VMCa, particularly in an engine-out situation, if the thrust ofthe remaining engine exceeds the Maximum Allowable Thrust equationabove. One or more body rate yaw sensors are used to detect the onset ofadverse yaw and the controller will then initiate the haptic crew alertto provide an additional margin of safety to compensate for weight orconfiguration. The haptic vibration is direction sensitive, such that itwill increase the force necessary to further advance the throttle inover speed, over-torque, or over-temperature. The haptic vibration canbe configured to hinder further advance and deliberately retard thethrottles until the exceedance is cleared. Also, the throttles will behindered from further reduction with an under-speed or AOA warning anddeliberately advance to eliminate an impending hazardous condition.

An automatic thrust control may be user enabled in the takeoff mode thatis initiated by a loss of an engine, with the airspeed below VMCa+3knots. The automatic control will retard the operating engine to athrust/torque defined by the above equation with the yaw sensor input.The computer monitors the yaw input and if the yaw exceeds 5 degreeswhen in OEI and at or below VMCa+3 IAS, the computer reduces the thruston the good engine, to mitigate the yaw.

The autothrottle provides automatic speed selection that can be useractivated to automatically set an appropriate maneuvering speed forturbulence penetration and/or Vref for approach speeds based on grossweight.

In one embodiment, simultaneous speed selection of the autothrottle andAutopilot speed hold is not permitted. If the autothrottle detectssimultaneous attempts to control speed-on-elevator, the autothrottlewill disconnect with a visual alert and a headphone audio alert. In apreferred embodiment, the audio alert is at about 1000 Hz.

As discussed above, the autothrottle is configured to adjust forwindshear. Windshear Sense functionality is provided by monitoringground speed (GS) versus airspeed (IAS) and ambient temperature (SAT).When the aircraft is in landing configuration with gear and flapsdeployed, a rapid increase of IAS vs GS disconnects the autothrottle toprevent automatic thrust reduction under the control of the autopilot inresponse to detection of a sudden increase in IAS resulting from windshear. The disconnect alerts the flight crew with and audio and/orvisual alert.

According to one aspect of the invention hot-starts are prevented. If anengine is started when it is above a certain temperature, there is arisk of engine damage. The autothrottle controller will receivetemperature measurements and prevent engine starts in certainconditions. For example, if the temperature exceeds 500° F. the enginewill be prevented from starting. Preferably the starter will turn on toblow air through the engine, which cools the engine. As the air isblowing through the engine, the fuel valve remains closed to preventfuel from entering the engine so it cannot start. Once the temperatureof the engine is below the cutoff temperature the fuel valve can openand the engine can be started.

Preferably, the temperature of the combustion is monitored to make surea maximum temperature is not exceeded. This temperature monitoring canalso be used during flight to control and maintain engine temperature.When a maximum temperature is reached, the autothrottle changes to atemperature control mode. For example, at 18,000 feet, power iscontrolled as a function of temperature so that the temperature ismaintained at a setpoint. In one embodiment, the operating setpoint maybe 720° F. Torque, temperature, and speed are adjusted to stay at orbelow the desired setpoint.

In one embodiment, ADSB data of a first plane, called the lead plane, isused by the autopilot to guide the operation of a second plane, calledthe follow plane. FIG. 7 is a schematic representation of a segment offlightpath from A to B for a first plane 100. The flightpath of thefirst plane 100 will be followed and mimiced by a second plane 100. Theautothrottle of the second plane 200 uses the ADSB data output from thefirst plane 100 to precisely “follow” the first plane and therebymaintain a desired distance, spacing, path, airspeed, and/or operatingmaneuvers between the first and second planes. The ADSB data used by theautothrottle is the same ADSB data seen by air traffic control and otherplanes in normal operation. For example, plane 200 can be instructed tofollow two miles behind plane 100. Plane 200 will “follow” each segment700-760 of the flightpath of plane 100 matching speed, altitude,heading, and the like. Because the second plane is “following” the firstplane, a desired or predetermined geometry between the planes ismaintained and, therefore, a tightening-up of air traffic can berealized.

As shown, there are seven segments between A and B. At each of thesesegments, plane 100 varied its speed, heading, altitude, or the like. Asplane 200 reaches each of these segments, and each location within eachsegment, plane 200's autothrottle, using the ADSB data from plane 100,mimics plane 100. In operation, the autothrottle functions as anautopilot using the lead plane 100 to control the follow plane 200.

The herein-described and other embodiments of the inventive system, withlittle or relatively little modification, can also be applied to theautomated control of aircraft flight control systems and elements otherthan the engine throttle controls. For example, the arrangement 10 canbe connected or coupled, instead of to the throttle lever, to aircraftcontrol surface elements such as the ailerons, trimtab(s), horizontalstabilizer and rudder to auto-adjust the positions of these flightcontrol surfaces as part of or under the control of the aircraft'sautopilot system.

Although example embodiments have been shown and described in thisspecification and figures, it would be appreciated by those skilled inthe art that changes may be made to the illustrated and/or describedexample embodiments without departing from their principles and spirit.

What is claimed is:
 1. An autothrottle system for an aircraft,comprising: a motor configured to impart rotational movement to a shaftextending from the motor, the motor being mounted on a support; anactuator assembly operatively connected to the shaft and to anattachment end of a throttle lever, the throttle lever having a controlend, opposite to the attachment end, to which manual force can beapplied; a position sensor operatively connected between the motor and amoving portion of the actuator assembly; and an electronic controllerconfigured to control the motor to cause movement of the throttle leverso that the motor moves the actuator assembly along the shaft based atleast in part on at least one of position information received from theposition sensor and an engine operating parameter monitored by thecontroller, wherein when a condition exists such that an actual engineperformance differs from a preferred engine performance, theautothrottle advances or retards the throttle lever in a regulatedmanner for optimal performance of the engine over different regions ofengine power output.
 2. The autothrottle system of claim 1, wherein theposition sensor is an optical sensor.
 3. The autothrottle system ofclaim 1, wherein the controller is configured to cause the throttlelever to vibrate, thereby providing haptic feedback to a user under adefined condition.
 4. The autothrottle system of claim 1, wherein theposition sensor comprises a linear potentiometer.
 5. The autothrottlesystem of claim 4, wherein the controller is configured to monitor oneor more of air speed, ground speed, and external temperature todetermine a windshear condition.
 6. The autothrottle system of claim 5,wherein the controller is configured to disconnect the autothrottle whenthe windshear condition is detected to prevent automatic thrustreduction.
 7. The autothrottle system of claim 1, wherein the controlleris configured to monitor multiple engine parameters to detect a loss ofan engine and to compute an amount of rudder authority loss due to areduction of airflow over a rudder.
 8. The autothrottle system of claim7, wherein the controller is configured to adjust yaw by varying anecessary reduction in thrust from a remaining engine by a relationship:Max thrust*(IAS/(Vmca+3)){circumflex over ( )}2, where IAS is indicatedair speed and Vmca is a minimum controllable air speed with the lostengine.
 9. A method for operating an autothrottle system for anaircraft, comprising: monitoring an engine temperature; determining ifthe temperature is above a setpoint; and when the temperature is abovethe setpoint: preventing engine starting; directing air to the engine toreduce engine temperature; and when the temperature reduces below thesetpoint, allowing the engine to start.
 10. The method for operating anautothrottle according to claim 9, wherein the engine is prevented fromstarting by stopping fuel flow to the engine.